How to construct a cube louver (Acoustat)

Could someone give me some insight into how Acoustat types are constructed. I believe I understand most of it.
what I'm mostly confused on is.
Do you make one side of a cube louver by applying the wires to the louver, apply the spacers to the cube louver, then glue the stretched membrane to the spacers, repeat for the back side cube louver.
I thought the Acoustat was somewhat dis-assembleable? If so, this would be permanent.
Is there a better way?
Thanks
Paul
 
The flat surface you see is the spacer. Acoustat used rigid plastic for these and the whole "sandwich" was glued together -- I have seen a series of pictures online that covered the whole process, but I can't remember the site.

I have never tried to take a panel apart, but I guess these pictures prove it can be done.
 
You might want to consider using acrylic louvres rather than the much cheaper styrene louvres. The acrylic will cost a lot more but the quality of the material is much higher and will be longer lasting. You can practice on styrene louvres and then do your final build with acrylic. Note you will have to use different adhesives and solvents than you do with the styrene. If you are doing a simple proof of concept experiment or you don't have a lot to spend then simply use the styrene. It will give you acceptable results and last a long time. The advantage to the acrylic material is that it is much stronger is better self damped and is more stable and will not get brittle with age as the styrene does.
Acoustat panels were not intended to ever be disassembled. With the acrylic you can easily go with a 3/8 inch thick louvre rather than the 1/2 inch styrene Acoustat used. Styrene louvre is also available in 3/8 inch thickness which works well too. If you use a wire with a thinner but stronger dielectric then you can use more wires per inch than Acoustat did which will yield a more efficient panel. You can use threaded rod to make a winding jig. !/4 - 20 threaded rod will give you 20 wires per inch perfectly spaced. If you just want to go with 5 -6 wires per inch as Jim did then just drill holes in the end row of the louvre and thread the wire. Not my first choice but it works.
You could also try drilling small holed into the end row of the louvre through both parallel walls of the first cube then insert a 3/4 inch finishing nail into the drilled hole and use that as a solid hook to wrap the wire around (you will need one nail for each loop of wire so say six per inch). Once the wire has been bonded down simply pull the nails out and the adhesive will hold the wires in place.
 
I've only had experience with Acoustat for about six weeks to two months now but here are my observations nevertheless.

First: Acoustat plastic louver panels look like they should not work at all and are truly an unlikely creation considering how most Estats are made today IE metal stators. I know this may sound like and ignorant statement to those familiar with the history of stats, but to the uninitiated it seems like an "unlikely and ponderous craft".

Second: they do indeed sound incredible. Incredibly smooth and more dynamic than comments I have heard previous to hearing them and then picking up a few sets of different models. They make bass. Deep bass into the 30's.

Third: The louver/wire loop grid construction is both brilliant and compromised. As much long term durability as these have proven to have, every single loose panel (out of the speaker) I have inspected has several problems and most seem to be associated with the glue-up process and the plastic construction materials.

Mechanically as a structure even when brand new and in a working set of speakers it is my contention that the panels physically cannot maintain rigidity under the acoustic force that these panels are capable of. Simply put the grid itself vibrates and distorts. This also could cause many electrical reactances that I am not qualified to analyze. But suffice to say that more rigid construction would be a great advantage to the "seminal" design of the original Acoustat panel.

Furthermore, I have seen glue seams partially or even fully split on the long sides and of course the known loose wires that come unstuck to the grid causing several "buzzing" or vibration conditions to occur. I have not had enough time with these to fully "see" with my eyes all these problems, but with the stack of used panels I have I'm sure to be tracking down little annoyances for awhile yet.

Lastly (for this post at least) Every panel has wrinkling in the corner of the mylar that is near the electrode connection to the panel. Looking at the construction photos on the TAC site, the wire and self adhesive metal tape that is used to secure the wire to the dark colored static coating is the probable cause/problem. I can make a bet that the "relaxing" of this compound "stack" of dissimilar materials and adhesives as well as the frame glue loosening is causing the corner wrinkle to occur. Later panels in the Spectra series I have not seen so I do not know if that problem was fixed in later model of the same panel.

I write all this detail because I believe that a truly un-compromised, 8 or 9 inch by 45 inch Acoustat panel has not been tried. Most have gone the route of smaller panels and "segmenting" the diaphragm into smaller subsections. I believe it would be a worthwhile goal to produce a much "better" and improved Acoustat type panel with much more rigid structure and the same or similar electrical and physical geometry that would allow a truly full volume, full range presentation from this fine sounding design, and not have to deal with the little niggling problems that the aging panels present. The volumes I played a pair of Model 3 at truly astounded me, and the smoothness and coherency at those volumes as well as deep bass were a surprise to me. However loud bass transients caused some "snap, crackle, and pop", yet I do not think that the speakers were necessarily arcing especially since I was sure that there were some stressful buzzing doing a mild sinewave sweep from 30Hz to 300Hz. I think more rigidity and an improved insulation might help.

Also in another thread I asked if anyone knew just what the coating mixture on Acoustats are and nobody seems to know. The TAC site is vague but describes it as carbon black and dissolved polymers. Some place write that the coatings resistance was changed to better hold a constant charge. With all the good press that King Estats from China are getting at $6K to $8K per set I'd thing a "BETTER" Acoustat sounds like a fairly easy and cheap way to DIY a really nice stat. A clear "see through" speaker that needs a "CONE" to have 30Hz bass does not sound like my cup of tea. The bass that 3 panels per side of 30 year old Acoustats has shown me enough that you can build a full range stat and not need it to be 8 feet tall and 4 feet wide and cost 20 grand. Besides most of us do not have rooms big enough for Sound Lab. I'll follow this thread and share what I learn as I tear apart a bad Acoustat panel.
 
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first the wire /grid stator design that Jim Strickland came up with was and is a brilliant piece of design work and it does a far better job than one would expect. You need to go back and look at what the retail price was of these unit to partially understand why specific design choices were made. The speakers were very inexpensive too much so as the company never made enough money and eventually went bust as a result.
As far as longevity and build quality goes Acoustats are the best that have ever gone to market. That's not to say that they could not be better but they delivered the goods in spades and most are still running.
Regarding repairs of loose stator wire you can use Testors model cement which is specifically designed for styrene they also have a citrus based cement which is more expensive but is totally non toxic which is nice and it works well. Use a thin wire to wrap the loose wire back into position twisting tight from the outside of the grid. Make sure the wire you use to pull the stator wire into place is not directly over the point where you need to apply your fresh glue. Several applications are usually required to get the stator wire locked well into place then remove the twist tie wire ad move on to your next repair. Please note that this is an ok fix if the stator wire has not jumped too far out of its home spot. Sometimes stator wires that pop loose actually make contact with the diaphragm and if this happens on the conductive coating side then you will most certainly have arc holes in the insulation of the stator wire. Getting the wire back into place and bonded down is good and help a lot but you have to understand that this is a patching process not a full repair. You are patching things up not repairing them. Sometimes this kind of fix does the job but you cannot count on that. These are old worn speakers and you have to keep that in mind.
The reason for the wrinkles in the corners of the diaphragm is simple. These diaphragms are made of DuPont Mylar HS65, which is a 0.65 mil thick heat shrink Mylar. The film is shrunk to tension and will over time and use stretch and get loose in the corners where the most tension is. You can re tension the diaphragms to as new tension with a heat shrink gun (carefully).
There is no issue with the resistive coating used from a physical point of view it is the best bonding coating I have ever seen though it is heavy. The coating is not as resistive as one would like but "thems the breaks". It sticks like wet poop to a blanket which is no small feat considering the blanket is Mylar with a surface tension of about 45 dynes per cm sq that's smoother than plate glass. This compound was made by a chemist who worked for one of the big magnetic tape manufacturers and he never told anyone what it was and when he died Acoustat had a heck of a time to replace it. Newer coatings are available which are far more resistive which is good or you can go the old tried and true method and used the nylon coating that Quad used the recipe is on line in a number of places. That will get you into the gig ohms of resistance and last a long long time.
There are lots of ways to modify an Acoustat to improve it but most are a lot of work and that effort is better spent on designing and building a new and better panel. You want many times more wires per inch to increase efficiency. You want to keep the DCR of your stators as low as possible which means connecting them electrically at each end. This can be done on an Acoustat to benefit but it is a genuine PITA to do I have done a bunch of these but it is not fun and you cannot get paid enough for the grief. Building new panels with Acrylic louvre is the way to go stronger better damped easier to work with easier to glue way longer life span. You can buy louvre in 1/2 inch thickness (with 1/2 x 1/2 cube dimensions) and you can get it in 3/8 inch thickness also with 1/2 x 1/2 square openings. The thinner material to me is better. If you use 3/8 Acrylic the stator will be as strong or stronger than the factory 1/2 inch styrene units. To your concerns of strength yes the panels could be stronger but they are better than a flat perf metal stator by a good margin and only a curved perf metal stator is really stiffer but then it has issues of its own. I have seen a set of Acoustat 2 plus 2 frames which had been wedge clamped to the ceiling to keep them rigid actually crack the 1 inch thick MDF frames of both speakers exactly in the middle of the frames (on both sides) where the two vertically stacked panels meet. If I had not seen this with my own eyes (I repaired these myself) I would not have believed the story. I have also seen the panels actually tear the lag bolts used to mount the panels out of the fir strapping in the frames. These things are very strong. Could they be better? Yes. Would they benefit from improvements? Yes. It is a lot of work but I think that the work is justified.
I do not believe that ESL's should be used for making bass. That's not to say I don't think they can make bass because they can. It is just that it is not a realistic or practical from either a domestic or performance point of view. You can make better cleaner deeper and physically smaller bass cabinets with a dynamic driver and do it for less expense. You end up with better overall performance and far less compromise than going full range ESL. A tall line source ESL which is narrow will provide very good horizontal dispersion and image. I would not build as wide as Jim did as he was trying to get bass out of his panels. You need to ditch the heavy HS diaphragms for thin stretched skins. You will get a stable panel (something the Acoustat had issues with) more output and better dynamics along with improved distortion figures. You can make a stat make bass but it involves a lot of trade offs. Better to get the job done the easiest and cheapest way and obtain better results. Hybrids are the way to go as far as I am concerned. C grade Mylar and other polyester films are available to the diy builder down to 3 microns in thickness (6 is probably the most practical to work with though).
If you want to see if your Acoustats are arcing get close in the dark and play your torture test disk. I would bet you they are the PVC dielectric is simply past its prime in a very harsh environment it has done a good job it's just time for fresh panels. A close physical instection in good light will probably reveal a number of small tiny pin holes in your diaphragm which are easiest to see when they are in the area of the diaphragm covered by the black resistive coating. If you find any pin holes then you have physical proof that your panels are arcing. Wire stators are tricky to build and to keep the stator wire dead flat on the louvre surface is something you just have to learn by doing. Styrene louvres are not flat to begin with either so you can see that there are going to be issues with some panels just working better than others. The harder you push the panel as far as bass response goes these issues become more problematic. When you lighten up on panel excursion then those problems go away and you can concentrate on making your panels play louder not deeper.
If you want a boost for your speakers add a couple of extra multiplier steps to your HT supply and get the voltage after the load resistor up to about 5 Kv or more if your panels will take the extra charge. This only costs a few dollars and makes a big difference as does a good noise filter for the HT supply. Hope this has been of assistance. Regards Moray James.
 
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Yes MJ and thank you for all the advise and info.

Other questions. Can clear GE style "RTV" silicon be used to fill gaps like at the side seam where the bias wire hookup is at the mylar edge. IOW is clear silicone rubber sealant a good insulator? I've been zapped at the edge of a live panel. Just a shock not dangerous....just don't want the panel bias to "leak" off anywhere. Also is it a good idea to put a bead of silicone around the mylar edge inside where it meets the plastic frame? If silicone is no good what is?
 
Oh forgot.
I'm in the sign business and we have many types of adhesive vinyl and mylar products and coatings. Couldn't I fish a tiny slip of clear adhesive to cover up any pinholes? The added mass would be negligible. The adhesive properties of some of the products we use is extremely strong and the thickness is down to 2 mils with some films.
 
I should have mentioned that a very good compromise for a strong well damped panel would be to use a properly made insulated perf metal grid with an reinforcing grid of Acrylic louvre bonded to the outside surface (3/8 inch thick louvre will work well for this). You should pre treat the perf metal to remove sharp edges (an acid bath is probably the best method) and then make sure when you assemble make sure the smooth side of the perf metal faces in toward the diaphragm (this is the side where the punches push into the metal when the holes are punched). The best coating for the job is Nylon 66. The reason for this is that it is an excellent powder coat material with strong enough insulation qualities and more so because Nylon 66 has about the least amount of creep of any coating you are going to find. Creep is the term used to discribe the character of coatings to pull away from or "creep" away from sharp edges. sharp edges are where your coating will be the thinnest and so the weakest in terms of electrical insulation strength so creep is an important factor. There are better insulation materials but Nylon 66 will build up best at the edges of the punched holes and that is exactly where you will have the greatest electrical charge so it is where you need the most insulation. Since Acrylic louvre does not have the excessive plasticizer that Styrene louvre does you can glue it and paint it and everything stays put for ever. With styrene louvre there is so much plasticizer (and it varies greatly from batch to batch) that adhesive which sticks well for a while can simply float off as the plasticizer sweats out of the base material. It is junky material. That is why Jim Strickland did not use glue to bond the PVC stator wires. The liquis styrene material Acoustat used does not glu the wire down it actually encapsulates into place. The liquid styrene used was the consistancy of thick syrup made liquid by mixing methylene chloride with base stock styrene solids. The solvent then melts itself into the base styrene louvre and when the solvent off gasses you have a solid thin layer of styrene which is solvent welded to the base louvre material. It is a good idea but there are issues, the biggest is that methylene chloride is a very nasty solvent and if you have any heart issues you should not use it. Working with this solvent requires full ventilation and outside is best. Even in a garage with open doors the solvent levels will get very high. This should not be considered a safe solvent to work with if you do not have a full facial respirator and an air supply. It can result in serious problems and it is just not worth it unless you are prepared to take full precautions in using it. I can't under state this because diy types often blunder ahead into such projects without due concern, I know I have done this myself.
 
This is how I built mine seven years ago these pics are of the smaller version 3.25" x 9.75".
I also built larger ones that are 7.75" x 22.5".
I am now getting ready to build a 4 foot version.
I was not aware the this material is available in acrylic as i have been using the readily available styrene poduct,as it works good but I to am not happy with its mechcanical strength and rigidablity.
However,both sizes still sound great and haven't had and any major mechcanical problems after seven years,just use good adhesives is all.
Does any one have a source for the acrylic version of this material? jer
 

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I just saw you last post so I will answer here. The contact point of the diaphragm resistive coating to the small foil strip is usually not an issue. I have never found one that failed. If you are getting a little leakage to the outer edges of the panel you can avoid shock by not touching them (ha) but this is not usually an issue and a thin layer of silicon seal is not a bad idea. You should check to see it there is any diaphragm sticking out first and simply remove it with a sharp exacto blade. the reason for this charge bleeding is contamination on the surface of the diaphragm (coating side only). You can address this by using a a Q-Tip and some paint thinner and wash the clear half inch wide stretch of diaphragm around the outside of the resistive coating. There is simply a build up of cooking grease and or cigarette residue that has built up and collected dust and become conductive enough to carry the charge to the outside edge of the film where your trembling fingers await initiation to the world of working on electrostats. The solvent wash might well be enough to solve the shocking condition of handling the panels out of the frame while still charged up. You will want to invest in a high voltage probe to use with your hand held multi metre, that's a lot better than using your fingers to see if things are loaded. Say can't they pack a wallop? Just as a side not I would probably be more inclined to clean things up with paint thinner and then spray paint half a dozen wet coats of clear high gloss (greatest solids content) urethane on the panel edges. Yes this is a lot more work than silicone but it will most likely do a much better job and you wont have bits of silly cone flaking off and getting into your panels over the years. Silicone will stick but it will float right off any spot which sweats out plasticizer. More work I know just what you wanted to hear but this is like the old Fram Air Filter guy says "You can pay me now or you can pay me later". With high voltage if you don't do things right you will pay for it sooner or later.
Regarding pin holes in the diaphragm don't worry about them at all as they have zero impact on speaker performance no matter how big they get. When the stator pops an arc which jumps to the resistive coating because it looks like ground it simply burns a tiny pin hole in the Mylar diaphragm. This hole self cauterizes and it is extremely rare to ever see one of these split open and run so don't worry about them they are not an issue.
Glad to see that you are in the sign business and are adept at using solvents and adhesives for plastics. That said the very worst abuses and violations of safety issues surrounding solvent use that I have ever seen (multiple times and places) is in plastic fabrication shops. Please be careful you know better than most that these solvents and adhesives can destroy your health. Hope this answers your questions.
 
Moray, If I have this right, after glueing the wires to the louver,
all of the loops at both ends of the louver are cut, and then soldered together with the exception of the first wire going to the panel, which goes to the transformer.
This is a better arraingment than Acoustat's "one long wire"?
Paul
 
To answer your question all the stator wires are soldered together as one and running a wire from the transformer to both ends of the panel and connecting to the shorted stator wires is better again because you are now driving the stator length from both ends. You can modify an Acoustat this way by removing enough insulation off each stator wire to expose the wire itself then solder tagging a wire across and connecting to each wire of the grid. I don't recommend this as it is a P.I.T.A. if you cut the wire you have to patch it up and it's not much fun to do. sounds good but it is a LOT of work. So I warned you.
 
My design goal for this was to make a speaker that was both easy to drive and efficient. I am willing to give up bass and space if necessary.
If I understand the concept right, more wires per inch will increase sensitivity.
Some people use magnet wire. I take it they do this because it comes in extremely thin gauges, and you could wind many more turns/inch.?.

Also, I'd think that if all I really was interested in was above 400 Hz the width of the panel wouldn't matter as far as bass roll off/beaming.
If I make the speaker wider do I gain in either max spl, or more importantly to me, in increased efficiency.
Thanks
Paul
 
Yes you are right.
That is the reason I had come up with the concept of using window screen for a stator material.
It only cost around 25 cents per square foot,as wire cost $.03 to $.10 per linear foot.
One 1'x4' can cost as much as $60 per panel or more using wire,which approaches the cost of a perforated metal panel.
Not to mention the time to stretch and glue all of those wires.
And the mechinical stability of the panel from the tension of all of those wires is also in question?
I have found that wire wrap wire with kynar insulation can withstand over 10kv without a problem,but again cost is an issue.
It would probaly work good for a small panel,but I didn't find it cost effetive for a large one.
On all of my panels I used a d/s spacing between .050" to .070" with .0625" being the target and I don't seem to be having any issues with bass frequency's, as they are only 3.5" wide.
On my bigger panel however I did as they are 8" wide and 22" long.
By swapping out the .060" thick frames to .090" thick frames solved that issue, and by just raising the bias voltage seemed to makeup for the lost efficiency.
I was not able to investigat this further due to personal reasons (mentioned elsewhere on another thread) in 2003.
I am just now picking up where I had left off ,back then, like it was yesterday.
If you were to look up some of my posts you would find all of my recent research in great detail with lots of pics.
Surface area seems to be the greatest factor to consider.
For every doubling of surface area you get a 6db of gain.
I found this to be very true,by just using two small panels together instead of one almost renders my little 4.5" woofer useless except for the extreme lows.
Even at that it has a hard time keeping up and would probaly be a better match to my 8" subs.
Not bad for for two little 3.5" x 10" panels.
Which is why I have chosen the sizes I have ,was too investigate this, and utilize the material as efficiently as I can.
My bigger panels are roughly 4 times larger and this should give me a 12db gain over the ones I'm working with at the moment.
My next ones will be twice as long at 8" x 46" this should give me an extra 18db over what I started with.
I will also try a small vs large d/s spacing as well.
From what I understand a panel this size should produce some very good spl's once I get my poweramp issues solved. jer
 
Hi,

one can have different opinions about the acoustat ESL-Panels.

As a manufacturer of ESL I need to say that those panels were state of the art at that time. You shopuld consider that we talk about a construction which was designed in the middle of the 70's !!! Todaxy you would do some things better, but the principle is sophisticated.

If someone opens an Acoustat ESL, yes you might find several issues, but did you consider how old those panels are ? 15 ,20 or even 25 years ?

Deassemble a standard 3 way system, having this age, the spider of the woofer ist briddle or even completely broken, The dome tweeter is limited by an aged magnetoferrit fluid ans so on......

Capaciti